Vulcanization of rubber



Patented May 9, 1939 UNITED STATES PATENT OFFICE VULCANIZATION OF RUBBERJoy G. Lichty, Stow, Ohio, assignor to Wingfoot Corporation, Wilmington,Del., a corporation of Delaware 11 Claims.

This invention relates to a new class of compounds, the members of whichare valuable in the vulcanization of rubber. It relates, among otherthings, to a method of accelerating the processes of vulcanization byincorporating in the vulcanized stock certain chemical compounds whichnot only are comparatively easy to prepare but also impart desirablephysical properties to the vulcanized products. The compounds with whichthe invention deals are new in themselves and may be described assubstituted ammonium carboxy alkyl sulphides derived froml-mercaptothiazoles.

Mercaptobenzothiazole and various derivatives thereof have been knownheretofore to accelerate the vulcanization of rubber. For instance, inUnited States Patent No. 1,784,498 to Scott, there is described the usein rubber of the reaction products of dichlor acetic acid andmercaptobenzothiazole. The patent also discloses the alkyl estersthereof. Such compounds, while good accelerators, are not as strong asthe substituted ammonium carboxy alkyl di(benzothiazyl l-sulphides) ofthe present invention which may be employed either by themselves or inconjunction azole with the sodium or other water soluble salt of themono or dihalogenated fatty acid, subsequently acidifying the productand then reacting it with the desired amine. In certain cases theproducts form at once. In others, it may be nec- 5 essary to heat themixture for a short period of time or, in the alternative, to allow itto stand for several hours. Usually it is preferable to prepare theproducts in solution. The solvent may be any which is suitable,generally water or alcohol being desirable. Any water soluble metallicsalt of the reactants other than the sodium salts may be used, thecalcium salts being exemplary.

Where the halogenated fatty acid employed is acetic acid, R in the aboveformula is methyl; similarly, where butyric acid, for instance, isemployed, R is a propyl group. Generally, the halogen atoms attach mosteasily to the carbon atom alpha to the carbonyl group of the fatty acidand, thus, the mercaptan sulphur atom of the 20 mercaptothiazole will beseparated from the carbonyl group of the fatty acid by a singlecarbonatom. When the compounds are to be employed as accelerators ofvulcanization, such products will generally be found preferable to thosein with a basic accelerator. The substituted amwhich the carbonyl groupis separated from the monium carboxy alkyl 1110110 (benzothiazyl -Smercaptothiazole radical by more than one car- D Of this inventifln aremore Powerful than bon atom, although it will be understood that theOther a bfl y alkyl 1110110 z thiazyl l-sulinvention is not limitedthereto. Aformula illusp d s) ut generally qu the p enc f a trating thepreferable compounds of the invention basic accelerator to giveeffective acceleration. i th following:

Illustrative of the compounds which the inven- N O H R tion concerns isthe type formula s 11 AR o-s C(H)z-OON I\ v n s 1 H R (T-s),.-R-ooxwherein AR represents an ortho arylene radical wherein T is al-thiazylradical, n is one or two, of the benzene and naphthalene series n is oneR is an alkyl group and X is a substituted or two, R is an aliphaticradical and R. 15 hydromonium radical. X may be any substitutedamaliphatic Wlth R forms an alkylene monium group such as cham- IIllustrating the preparation of these com- H CH; E 02115 H CED-CH2 H Opounds is that of piperidinium carboxy methyl 1/ l/ l/ CH2 benzothiazyll-sulphide. This compoundis pre- I\ l\ l pared by suspending grams ofcarboxy methyl H H H H OHPCH H H benzothiazyl l-sulphide in a solutionof 18.7 45 etc. The compounds may be prepared by reactgrams ofpiperidine in cc. of ether. The mixing a l-mercaptothiazole, preferablyan alkali ture is then triturated, filtered and the product 7 metal saltthereof, with a substituted ammonium washed with ether. The product,piperidinium salt of a monoor dihalogenated fatty acid. An carboxymethyl benzothiazyl l-sulphide, melts alternative procedure is to reactan alkali metal at 126-127 C. and is obtained in an almost quan- 5 orother water soluble salt of a l-mercaptothititative yield. The reactionproceeds as follows:

OSGH20O0H+O HwNH o-s-omooorrrnonzw S/ S/ I i Ethylene di ammonium oxycarbonyl methyl benzothiazyl l-sulphide) is prepared similarly by addingslowly with stirring 12.5 grams of 95.8% ethylene diamine to asuspension of Q0 grams of carboxy methyl benzothiazyl l-sulphide in 400cc. of methyl alcohol. A precipitate forms" which, upon being filteredand recrystallizedfrom water, melts at 189-190 C. The reaction proceedsas follows:

Nears .The cyclohexyl amine salt of carboxy methyl benzothiazyll-sulphide is prepared; by adding 55 1 grams of cyclohexyl amine to asuspension of 112.5

grams of carboxy methyl benzothiazyl sulphide in 30000. of methylalcohol. Anexotherrnic reaction takes place, theresulting salt goinginto 1 solution and separating out oncocling; The re- Q sulting solid,when filtered ofi anddried, melts at 182 C. and weighs 147.3 grams. Theequation representing the reaction is as follows:

Substituted ammonium salts of carboiiy alkyl di(thiazyl l-sulphides) maybe prepared similarly by reacting the desired amine with the carboxyalkyl cli(benzothiazyl l-sulphide) or bylreacting' a substitutedammonium salt of the dihalog'enated fatty acid' With the desiredmercaptothiazole, preferably an alkali metal salt thereof. Thus, thedibutyl amine salt of carboxy methyl di(benZothiazyl l-sulphide) may beprepared by adding dibutyl amine to a suspension of carboxy methyldi(benzothiazyl l-sulphide) in methyl alcohol. The resulting product maybe'separated as described above. The reaction is as follows? The carboxymethyl di(benzothiazyl l-sulphide) is conveniently prepared by reactingthe sodium salt of mercaptobenzothiazole with the sodium salt of dichloracetic acid and thereafteracidifyingthe product.

Other compounds of the invention are piperidinium carboxy methyldi(benzothia zyl 1-sulphide), morpholinium carboXy methyldi(benzothiazyl l-sulphide), methyl ammonium carboxy methyl benzothiazyll sulphide, morpholinium carboxy methyl benzothiazyl l-sulphide, diisopropyl ammonium carboxy methyl di(benz0- thiazyl l-sulphide); isoamyl ammonium carboxy methyl benzothiazyl l-sulphide, dicyclohexylammonium carboxy methyl benzothiazyl l-sulphide,

dicyclohexyl ammonium carboxy methyl di- (benzothiazyl l-sulphide),phenyl ammonium carboxy methyl di(ben zothiazyl l-sulphide), benzylammonium carboxy methyl di(benzothiazyl l-"sulphideh beta phenylethylene ammonium carboxy methyl di(benzothiazyl l-sulphide), tetrahydroalpha I"urfur'yl ammonium carboxy methyl benzothiazyl l-sulphide,tetrahydro alpha fur-furyl ammonium carboxy -methyl'di(benzothiazylI-sulphide), ditetrahydro alpha, furfuryl ammonium carboxy methyldi(benzothiazyl lsulphide) and ditetrahydro alpha furfuryl ammomumcarboxy methyl b'enzothiazyl l-sulph'ideL i Others. (are theparaphenylene diamine'salt of ca'rboxy, methyl benzothiazyl l-sulphide,the para phenylene diamine salt of carboxy methyl di- (benzothiazyli-sulphide) the diphenylguanidine salt of carboxy methyl di(benzothiazyll-sulphide), dibenzyl ammonium. carboxy methyl benzothiazyl l-sulphide,and furfuryl ammonium carboxy methyl di(benzothiazyl l-sulphide). Stillothers are diethyl ammonium alpha carboxy propyl benzothiazyll-sul'phide, piperidinium am monium alpha carboxy propyl benzothiazyl 1-sulphide, cyclohexyl ammonium alpha carboxy propyl benzothiazyll-sulphide, and butyl ammonium alpha carboxy propyl benzothiazyll-sulphide, One. method of preparing these latter materials is to reactthe amine with alpha carboxy propyl benzothiazyl l-sulphide whichisprepared V by dissolving in water one mol of the sodium salt of alphabrom butyric acid and mixing the resulting solution with an aqueoussolution of one mol of the sodium salt of l -mercaptobenzothiazqle andacidifying to form the free acid. The formula H can of alpha carboxypropyl benzothiazyl l-sulphide is believed to be as follows:

It will of course be understood that any other mercapto thiazole may beemployed in the practice of the invention, examples being l-mercaptoalpha naphthathiazole, l-mercapto beta naphthathiazole, l-mercaptol-nitro benzothiazole, lmercapto 5-nitro benzothiazole, l-mercapto 4-chlor benzothiazole, l-mercapto 5-chlor benzothiazole, l-mercaptoB-phenyl benzothiazo-le, 1- mercaptothiazole, l-mercapto B-phenylthiazole, l-mercapto 3-methyl thiazole, l-mercaplto 3- methylbenzothiazole, the l-mercapto tolyl thiazoles, the l-mercapto Xylylthiazoles, l-mercapto 5-amino benzothiazoles, l-mercapto 5-ethoxybenzothiazole, l-mercapto 5-methoxy benzothiazole and other halogen-,nitro-, hydro-xy-, alkoxy-, and amino-substituted arylenemercaptothiazoles.

The compounds to which the invention relates may be employed asaccelerators of vulcanization in substantially any of the standardrubber formulae, one found satisfactory being the following:

Parts by weight After vulcanization, physical tests on illustrativestocks so made up were run with the following results:

M k Nfodu luts Ult. tens. 1 8 cm. a Cure, time in mms. F. elong. mkgs/cm percent Ethylene diumi'nc salt 0] carbon methyl benzolhiazyll-sulphlde, 0.6 part; diphenylguanidlne, 0.2 part Dlphenylguam'dlne saltof CflTbDIjl/ methyl benzolhiazyl I-sulphlde, 0.5 part;dlphenylguanidlne, 0.2 part Piperz'dlnium carboxy methyl benzothz'azylI-sulphide, 0.5 part; dlphe'nz l guamdz'ne, 0.2 part These compounds,new in themselves, possess valuable properties as accelerators ofvulcanization. The substituted ammonium carboxy alkyl di(thiazyll-sulphides) may be employed either by themselves or in conjunction withother basic nitrogen-containing accelerators such as diphenylguanidine,diortho tolyl guanidine, diphenylguanidine oxalate, diphenylguanidinesuccinate, cyclohexyl ammonium fumarate, the acceleratingaldehyde-amines, the poly ethylene poly amines, and the like. Ingeneral, the substituted ammonium salts of the dihalogen fatty acid orderivatives of the mercaptothiazoles are more powerful accelerators thanthe substituted ammonium salts of the mono halogen derivatives.Consequently, with the dihalogen derivatives, activators will notusually be necessary, although they may be found desirable in certaininstances. With the mono halogen derivatives, on the other hand,activators are in most cases desirable.

Itis intended that the patent shall cover, by suitable expression in theappended claims, whatever features of patentable novelty reside in theinvention.

What I claim is:

1. The process which comprises vulcanizing a vulcanizable rubbercomposition in the presence of piperidinium carboxymethyl benzothiazyl1- sulphide having the formula 2. The process which comprisesvulcanizing a vulcanizable rubber composition in the presence ofdiphenylguanidine and an aliphatic amine salt of carboxymethylbenzothiazyl 1-sulphide, the free acid having the formula 3. The processwhich comprises vulcanizing a vulcanizable rubber composition in thepresence of a basic nitrogen-containing accelerator and a primary aminesalt of carboxymethyl benzothiazyl l-sulphide, the free acid having theformula 4. The process which comprises vulcanizing a vulcanizable rubbercomposition in the presence of a compound of the formula wherein R. andR are aliphatic radicals.

5. The process which comprises vulcanizing a vulcanizable rubbercomposition in the presence of a basic nitrogen-containing acceleratorand a compound of the formula wherein X is an organic ammonium radicalconnected through the nitrogen.

6. The process which comprises vulcanizing a vulcanizable rubbercomposition in the presence of a basic nitrogen-containing acceleratorand a compound of the formula TS-CH -(J-OX I wherein T is a l-thiazylradical and X is binary ammonium group connected through the nitrogen.

7. The process which comprises vulcanizing a vulcanizable rubbercomposition in the presence of a basic nitrogen-containing acceleratorand diphenyl guanidine carboxymethyl benzothiazyl 1- sulphicle havingthe formula.

8. The process which comprises vulcanizing a 9. A rubber product whichhas been vulcanized in the presence of a basic nitrogen-containingaccelerator and a secondary amine salt of carboxymethyl benzothiazyll-sulphide, the free acid having the formula 10. The process whichcomprises vulcanizing 2.

vulcanizable rubber composition in the presence of an amine salt ofacetic acid in which only one hydrogen atom of the methyl group linkedto the CO is replaced by a benzothiazyl l-thio radical.

11. A process which comprises vulcanizing a vulcanizable rubbercomposition in the presence of a basic nitrogen-containing acceleratorand an amine salt of acetic acid in which only one hydrogen atom of themethyl group linked to the CO is replaced by an arylene thiazyl l-thioradical and in which one of the other two hydrogen atoms of the methylgroup linked to the 00 may be replaced by an alkyl group, saidamines'being selected from the group consisting of the primary andsecondary aliphatic amines, the primary and secondary alicyclic amines,the primary aromatic amines, the primary and secondary aralkyl aminesand the primary and secondary furfuryl and tetrahydro furfuryl amines.

JOY G. LICHTY.

Certificate of Correction Patent No. 2,158,021. May 9, 1939. JOY G.LIOHTY It is hereby certified that errors appear in the printedspecification of the above numbered patent requiring correction asfollows: Page 1, first column, line 5-6, for the Word vulcanized readnnvnlcan'ized; page 3, second column, lines 32 to 35 inclusive, claim 3,strike out the formula and insert instead the following o-s-omcoon line68, claim 7, for guanidine read guanidininm; and that the said LettersPatent should be read with these corrections therein that the same mayconform to the record of the case in the Patent Oflice.

Signed and sealed this 1st day of August, A. D. 1939.

[SEAL] HENRY VAN ARSDALE,

Acting Commissioner (y' Patents.

